Adrian Ratiu c45a34e12e run-command: poll child input in addition to output ...

Child input feeding might hit the 100ms output poll timeout as a
side-effect of the ungroup=0 design when feeding multiple children
in parallel and buffering their outputs.

This throttles the write throughput as reported by Kristoffer.

Peff also noted that the parent might block if the write pipe is full
and cause a deadlock if both parent + child wait for one another.

Thus we refactor the run-command I/O loop so it polls on both child
input and output fds to eliminate the risk of artificial 100ms
latencies and unnecessarily blocking the main process.

This ensures that parallel hooks are fed data ASAP while maintaining
responsiveness for (sideband) output.

It's worth noting that in our current design, sequential execution
is not affected by this because it still uses the ungroup=1 behavior,
so there are no run-command induced buffering delays since the child
sequentially outputs directly to the parent-inherited fds.

Reported-by: Kristoffer Haugsbakk <kristofferhaugsbakk@fastmail.com>
Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2026-01-28 15:47:03 -08:00

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